For parallel current-sharing control methods for a conventional high-power switching power supply, such as a master-slave method, a mean value method, and a maximum current method, a maximum current or a mean current is fed back through a current bus, and an error is formed between the maximum current or the mean current and a current in the current bus itself, to adjust a module voltage reference, thereby realizing current sharing, as shown in FIG. 1. In the current-sharing methods, multiple control loops need to be connected in series, so that the system response becomes slower, especially when multiple power supplies are connected in parallel.
In the conventional current-sharing methods, a current bus is required. A module current signal should be integrated into the bus and meanwhile, a bus signal can be transmitted to the modules, to perform amplification of an error between the bus signal and a module current feedback signal, that is to say, signal transmission in current bus is bidirectional. In a scene of serious electromagnetic interference, differential transmission is desired to obtain a high common mode rejection ratio, but two transmitter-receiver sets are required in the differential transmission to enable bidirectional signal transmission, thereby undoubtedly increasing the costs of implementing current sharing through a current bus and the complexity of design and production.
For the purpose of improving load regulation and precision of an output voltage, a voltage control module generally needs to be placed outside a parallel system, as shown in FIG. 2, to perform error amplification on a set reference and a feedback signal of parallel voltage output terminals to generate a total control signal, where the total control signal is unidirectional and can be transmitted to submodules through a differential device as a control reference. If the foregoing conventional current-sharing control method is adopted, two control buses are required in the system to implement remote voltage compensation and module current equalization, thereby undoubtedly increasing the complexity and fault rate of the system.
Generally, the module current signal is integrated into the current bus through a diode or resistor, a current bus signal is directly transmitted to an input end of a module error amplifier, and multiple common grounded points exist in the modules, which possibly generates a ground wire loop current, so that a current-sharing loop and even the system are interfered very easily and thus the stability of the system becomes poor.
For many control systems, the current-sharing control method is desired to be implemented through both an analog circuit and a digital circuit and applied in both a switching power supply and a linear power supply, so the current-sharing control method needs to be implemented very simply and thus have high flexibility. However, the conventional current-sharing method is relatively complex.
In the foregoing conventional current-sharing control method and device, because of a slow system response, multiple control buses are required, which is adverse to differential signal transmission, so that a loop current is easily generated, the anti-interference capability is poor, and the circuit design, production, assembly, and debugging are complex; and the method and the device cannot be flexibly applied to other types of control systems, thereby having a limited application range.